Micropipetting
Hints & tips
Check your dispensing volume by pipetting and weighing water. This helps avoid errors caused by mistakes in setting the volume (often errors are caused by the decimal places!). Use your pipette to dispense your volume into a tared container on a balance and then calculate the actual pipetted volume (volume=mass/density). This is usually how the instrument is calibrated.
Never invert a pipette, as this can cause damage if liquid enters the pipettor.
Do not leave a pipette on its side with liquid in the tip as this will allow it to travel to the pipette barrel which will damage the pipette.
To get the most accurate volumes, you should aim to use a pipette that carries the lowest volume appropriate e.g. to pipette 80 uL you should consider using a P100 over a P200 and this will lead to a smaller error.
Handling smaller volumes can lead to larger errors so it is important to work precisely and accurately. It can be the little things such as tips not loaded correctly that can lead to the wrong volume being pipetted. If you are unsure expel the liquid, check the tip is secure and then draw it up liquid again to check it reaches the same point in the tip.
It is easier (and usually more accurate) to transfer larger volumes e.g. rather than pipetting 5 uL, you could dilute the stock solution 10 times and pipette 50 uL instead.
Avoid pipetting quantities that exceed the limits of that pipette as this can damage/uncalibrate tthem. It can also lead to liquid being taken inside the pipette barrel, contaminating the end of the pipette and your sample.
You should always use a clean pipette tip when transferring different samples to avoid cross contamination - if you are unsure what has been in the pipette tip or it has touched the fumehood/lab bench it is always better to use a clean tip.
When changing volumes, look at the number dial face on to make sure it is aligned correctly.